There are a number of Kelly and Kelly et al patents on hingeless ventilators particularly designed for ventilating a cab or other compartment of a vehicle. Among those patents are U.S. Pat. Nos. 3,102,464, 3,358,576, 3,839,950 and 4,452,129, all for two-way ventilators having closure members openable in one direction to draw air into and in the opposite direction to exhaust air from a vehicle compartment. In each of these patents the ventilator has a frame attachable to a wall of a vehicle compartment about an aperture therein and a corresponding opening in the frame bounded by an outturned flange. Swingable between open and closed positions against an outside of the frame, the closure member in closed position has an inturned marginal flange surrounding and overlapping the frame flange and alternately engageable with the frame flange on opposite sides of the frame opening for substantially fixing the swinging axes of the closure member.
In U.S. Pat. Nos. 3,839,950 ('950) and 4,452,129 ('129), rollers connected for movement in unison to the closure member, ride on guide members fixed to and instanding from the frame beyond opposite ends of the frame opening for selectively positioning the closure member relative to the frame. In both patents a tensile force holds the closure member against the frame, with the difference that in patent '129 the force is derived from compression of elastomeric rollers, while in patent '950 the rollers are on opposite ends of a spring rod and the tensile force is derived from connecting the rod intermediate its ends to the closure member for flexing or bowing toward the closure member.
The concern of the present invention is an improvement on the spring rod hingeless ventilator of patent '950.